The women were found naked between 2 and 12 December
A second man has been arrested over the murders of five prostitutes found dead in the Suffolk countryside.
He was named locally as Stephen Wright, 48, and is suspected of killing Gemma Adams, Anneli Alderton, Tania Nicol, Annette Nicholls and Paula Clennell.
The first suspect, Tom Stephens, 37, was arrested on Monday.
Magistrates have granted police an extra 36 hours to continue questioning Mr Stephens. Mr Wright was arrested at his Ipswich home earlier.
Forensic teams have been searching an address in the London Road area of Ipswich where Mr Wright was arrested.
Det Ch Supt Stewart Gull said: "The man is currently in custody at a police station in Suffolk where he will be questioned about the deaths later.
"Police will not be naming the police station where the man is being held."
Former special constable Mr Stephens was arrested at his home at Trimley St Martin, near Felixstowe.
He remains in custody at an unidentified police station in Suffolk. Detectives can hold him for up to 96 hours, that is up to Friday evening.
"As legal proceedings are active, Suffolk Police will not be issuing any further comments or appeals at this stage," Mr Gull said.
Police have not confirmed or denied the identities of the people in custody.
Inquests into the deaths of four of the five prostitutes found murdered near Ipswich are to open on Wednesday, a police spokesman said.
The inquests into the deaths of Miss Nicol, Miss Alderton, Miss Nicholls and Miss Clennell will be opened and adjourned by a coroner at Ipswich Crown Court, said a police spokeswoman.
The inquest into the death of Gemma Adams was opened last week.
Forensic scientists and police teams have been carrying out searches at Mr Stephens' home, in Jubilee Close, and his mother's home in the market town of Eye, Suffolk.
Mr Stephens has said he knew the women who died but he denies any wrongdoing.
Speaking in an interview with BBC News last week for background purposes, Mr Stephens said he "was probably the closest thing Tania [Nicol] had as a boyfriend".
Mr Stephens, who worked for Tesco in Martlesham, said he had spoken to Miss Nicol's mother in the days following her disappearance.
He said he had known 19-year-old Miss Nicol for about six months but had known Miss Adams for 18 months, "about as long as I've known any of the girls".
Police interviewed him at his home earlier in the investigation and had taken his mobile phone and laptop computer, he added.
The five dead women were all found naked in rural settings, within 10 miles of Ipswich and close to the A14.
The body of Miss Adams, 25, who went missing on 15 November, was found in a brook at Hintlesham, Suffolk, on 2 December.
Miss Nicol's body was found by police divers at Copdock Mill, near Ipswich, on 8 December.
The body of Miss Alderton, 24, from Essex, was found in woodland in Nacton, near Ipswich, on 10 December.
On 12 December detectives found the bodies of Miss Clennell, 24, and Miss Nicholls, 29, near the village of Levington.